In the tumultuous year of 1922, set against the backdrop of an unnamed country south of Mexico engulfed in revolution, we follow the gripping tale of Emmet Keogh, a fervent Irish patriot and skilled political assassin. Coerced into an unconventional and dangerous task, he must transport a truck brimming with Scotch whiskey for the enigmatic English gunrunner, Jennings. During his perilous journey, he encounters the kindly Father Oliver Van Horne, an American Catholic priest who finds himself in a bit of a predicament with a flat tire and later, a car trapped atop some rocks. This seemingly trivial meeting soon evolves into something extraordinarily significant.
As fate would have it, upon reaching his intended destination, Keogh discovers that the man awaiting the whiskey delivery has met an untimely end at the hands of the ruthless Colonel Santilla and his men. Even more alarmingly, these men are poised to commit heinous acts against a mute Aymara Indian woman named Chela. When Keogh heroically intervenes to stop their vile intentions, he becomes the target of retribution, marking himself for execution. However, just in the nick of time, Van Horne enters the fray, wielding a machine gun and methodically eliminating Santilla's men. Alas, one rogue escapes, hastening to inform Santilla of their escape, and despite their valiant effort, Keogh, Van Horne, and Chela find themselves captured.
In a terrifying twist of fate, Santilla subjects them to a mock execution—an agonizing moment where their lives hang by a thread. However, the crafty Colonel offers them a chance for survival: they must assassinate Tomas de la Plata who resides under tight security in Mojada, a region firmly under his control. Tempted by the prospect of sharing a handsome sum of $53,000 recently unearthed in Van Horne's suitcase, Keogh and Jennings accept the perilous mission. Santilla has cleverly arranged an invitation for them, allowing them to masquerade as mining company employees eager to delve into potentially lucrative silver mining operations.
The plot thickens as Keogh crosses paths with Aymara Chief Nacho, rekindling his connection with Chela, who surprises him with a meaningful necklace—unbeknownst to him, this gesture signifies their unsanctioned matrimony within her matriarchal society where women dictate their partners. Upon reaching the hacienda of de la Plata, van Horne dedicates himself to cleaning the church with the help of an orphan choirboy named Pablito, while Keogh and Jennings are invited to dine under the watchful eye of de la Plata, a man with a notorious disdain for priests, having lost several in his town.
The unfolding events lead to a cave-in at the mine that Keogh and Jennings were ostensibly inspecting, forcing them into a rescue operation alongside Van Horne to save Senora de la Plata and several miners. A bold plan unfolds as Van Horne intends to lure de la Plata into an ambush by announcing a mass for the deceased miners at 4 p.m. However, when Senora de la Plata arrives to join the mass, Van Horne is compelled to abort this carefully devised plan, fearing for the priest's safety. Under the influence of his mother’s plea, de la Plata spares Van Horne, albeit with restrictions against performing any priestly duties—a fate that reflects the terrible history of violence subjected to his family and community by Santilla's men.
Unwavering, Van Horne attempts once more, planning to hold a procession, promising the townspeople a plethora of spiritual services, hoping to inspire gratitude and solidarity in their fight against de la Plata. Secrets unfold; it becomes clear that Van Horne was once a true priest, disillusioned by a corrupt bishop. As tension mounts, the following morning brings violence as some of de la Plata's men are killed, but the leader narrowly escapes.
In a chilling turn of events, Nacho arrives, battered and bloodied, bearing heart-wrenching news about hostages taken by de la Plata, including Chela and Pablito, with threats looming over their lives. Each half hour, another hostage's fate hangs in the balance. The situation escalates tragically when Jurado, de la Plata’s second in command, callously murders Pablito before Van Horne’s eyes, a moment that ignites a fierce resolve within the priest, prompting him to surrender himself to save the lives of the innocents.
Van Horne’s capturing culminates in a chaotic confrontation where he mistakenly kills a lookalike of de la Plata. Yet, in a daring bid for heroism, Keogh and Nacho, along with several Aymara men, orchestrate a rescue mission for Chela, strategically using grenades to blast through the entrance of their prison. A chaotic fight ensues, showcasing the valor and desperation of all involved, as Jennings, despite sustaining mortal wounds, manages to unleash destruction upon their captors.
In the midst of the chaos, de la Plata finds himself face-to-face with Keogh, ready to enact his vengeance until a twist of fate sees him shot by none other than his own mother, leading to a climactic struggle. As the dust settles, Van Horne, having endured unimaginable trials, manages to topple a cross upon de la Plata in a fit of righteous fury, bringing an end to a dark chapter as the church bells sound in the distance, signifying hope and resilience amid the ruins of chaos.
